leandrof/linux
1
0
Fork 0
forked from Minki/linux
Code Issues Pull Requests Packages Projects Releases Wiki Activity

netfilter: nf_ct_sip: support Cisco 7941/7945 IP phones

Browse Source 
Most SIP devices use a source port of 5060/udp on SIP requests, so the
response automatically comes back to port 5060:

    phone_ip:5060 -> proxy_ip:5060   REGISTER
    proxy_ip:5060 -> phone_ip:5060   100 Trying

The newer Cisco IP phones, however, use a randomly chosen high source
port for the SIP request but expect the response on port 5060:

    phone_ip:49173 -> proxy_ip:5060  REGISTER
    proxy_ip:5060 -> phone_ip:5060   100 Trying

Standard Linux NAT, with or without nf_nat_sip, will send the reply back
to port 49173, not 5060:

    phone_ip:49173 -> proxy_ip:5060  REGISTER
    proxy_ip:5060 -> phone_ip:49173  100 Trying

But the phone is not listening on 49173, so it will never see the reply.

This patch modifies nf_*_sip to work around this quirk by extracting
the SIP response port from the Via: header, iff the source IP in the
packet header matches the source IP in the SIP request.

Signed-off-by: Kevin Cernekee <cernekee@gmail.com>
Acked-by: Eric Dumazet <eric.dumazet@gmail.com>
Cc: Patrick McHardy <kaber@trash.net>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>
This commit is contained in:
Kevin Cernekee 2012-12-17 18:33:58 +00:00 committed by Pablo Neira Ayuso
parent 247fa82be1
commit 7266507d89
3 changed files with 44 additions and 3 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

3
include/linux/netfilter/nf_conntrack_sip.h
View File

@ -4,12 +4,15 @@
#include <net/netfilter/nf_conntrack_expect.h>
#include <linux/types.h>
#define SIP_PORT 5060
#define SIP_TIMEOUT 3600
struct nf_ct_sip_master {
unsigned int register_cseq;
unsigned int invite_cseq;
__be16 forced_dport;
};
enum sip_expectation_classes {

17
net/netfilter/nf_conntrack_sip.c
View File

@ -1440,8 +1440,25 @@ static int process_sip_request(struct sk_buff *skb, unsigned int protoff,
{
enum ip_conntrack_info ctinfo;
struct nf_conn *ct = nf_ct_get(skb, &ctinfo);
struct nf_ct_sip_master *ct_sip_info = nfct_help_data(ct);
enum ip_conntrack_dir dir = CTINFO2DIR(ctinfo);
unsigned int matchoff, matchlen;
unsigned int cseq, i;
union nf_inet_addr addr;
__be16 port;
/* Many Cisco IP phones use a high source port for SIP requests, but
* listen for the response on port 5060. If we are the local
* router for one of these phones, save the port number from the
* Via: header so that nf_nat_sip can redirect the responses to
* the correct port.
*/
if (ct_sip_parse_header_uri(ct, *dptr, NULL, *datalen,
SIP_HDR_VIA_UDP, NULL, &matchoff,
&matchlen, &addr, &port) > 0 &&
port != ct->tuplehash[dir].tuple.src.u.udp.port &&
nf_inet_addr_cmp(&addr, &ct->tuplehash[dir].tuple.src.u3))
ct_sip_info->forced_dport = port;
for (i = 0; i < ARRAY_SIZE(sip_handlers); i++) {
const struct sip_handler *handler;

27
net/netfilter/nf_nat_sip.c
View File

@ -95,6 +95,7 @@ static int map_addr(struct sk_buff *skb, unsigned int protoff,
enum ip_conntrack_info ctinfo;
struct nf_conn *ct = nf_ct_get(skb, &ctinfo);
enum ip_conntrack_dir dir = CTINFO2DIR(ctinfo);
struct nf_ct_sip_master *ct_sip_info = nfct_help_data(ct);
char buffer[INET6_ADDRSTRLEN + sizeof("[]:nnnnn")];
unsigned int buflen;
union nf_inet_addr newaddr;
@ -107,7 +108,8 @@ static int map_addr(struct sk_buff *skb, unsigned int protoff,
} else if (nf_inet_addr_cmp(&ct->tuplehash[dir].tuple.dst.u3, addr) &&
ct->tuplehash[dir].tuple.dst.u.udp.port == port) {
newaddr = ct->tuplehash[!dir].tuple.src.u3;
newport = ct->tuplehash[!dir].tuple.src.u.udp.port;
newport = ct_sip_info->forced_dport ? :
ct->tuplehash[!dir].tuple.src.u.udp.port;
} else
return 1;
@ -144,6 +146,7 @@ static unsigned int nf_nat_sip(struct sk_buff *skb, unsigned int protoff,
enum ip_conntrack_info ctinfo;
struct nf_conn *ct = nf_ct_get(skb, &ctinfo);
enum ip_conntrack_dir dir = CTINFO2DIR(ctinfo);
struct nf_ct_sip_master *ct_sip_info = nfct_help_data(ct);
unsigned int coff, matchoff, matchlen;
enum sip_header_types hdr;
union nf_inet_addr addr;
@ -258,6 +261,21 @@ next:
!map_sip_addr(skb, protoff, dataoff, dptr, datalen, SIP_HDR_TO))
return NF_DROP;
/* Mangle destination port for Cisco phones, then fix up checksums */
if (dir == IP_CT_DIR_REPLY && ct_sip_info->forced_dport) {
struct udphdr *uh;
if (!skb_make_writable(skb, skb->len))
return NF_DROP;
uh = (void *)skb->data + protoff;
uh->dest = ct_sip_info->forced_dport;
if (!nf_nat_mangle_udp_packet(skb, ct, ctinfo, protoff,
0, 0, NULL, 0))
return NF_DROP;
}
return NF_ACCEPT;
}
@ -311,8 +329,10 @@ static unsigned int nf_nat_sip_expect(struct sk_buff *skb, unsigned int protoff,
enum ip_conntrack_info ctinfo;
struct nf_conn *ct = nf_ct_get(skb, &ctinfo);
enum ip_conntrack_dir dir = CTINFO2DIR(ctinfo);
struct nf_ct_sip_master *ct_sip_info = nfct_help_data(ct);
union nf_inet_addr newaddr;
u_int16_t port;
__be16 srcport;
char buffer[INET6_ADDRSTRLEN + sizeof("[]:nnnnn")];
unsigned int buflen;
@ -326,8 +346,9 @@ static unsigned int nf_nat_sip_expect(struct sk_buff *skb, unsigned int protoff,
/* If the signalling port matches the connection's source port in the
* original direction, try to use the destination port in the opposite
* direction. */
if (exp->tuple.dst.u.udp.port ==
ct->tuplehash[dir].tuple.src.u.udp.port)
srcport = ct_sip_info->forced_dport ? :
ct->tuplehash[dir].tuple.src.u.udp.port;
if (exp->tuple.dst.u.udp.port == srcport)
port = ntohs(ct->tuplehash[!dir].tuple.dst.u.udp.port);
else
port = ntohs(exp->tuple.dst.u.udp.port);